FCD: If you had to compile a list of the most important infographics in the history of western civilization, this cutaway chart of the 18th-century Brooks slave ship would rank right up there with Charles Minard’s flow map of the ill-fated Russian campaign of 1812 and pretty much anything by Ed Tufte.

Eye magazine has a fascinating account of how the drawing became a key visual weapon in the 18th- and 19th-century fight against slavery, as part of a larger feature on information design that changes minds. First published by British abolitionists in 1788, the diagram depicts a vessel of 400 slaves packed in cheek by jowl, some with just 2 feet and 7 inches of headroom. The Brooks was an actual ship that schlepped enslaved Africans to Liverpool, England, and typified the slave vessels of the era: The Regulated Slave Trade Act of 1788, which was designed to reduce deaths due to overcrowding on slave ships, allowed each man 6 feet by 1 foot 4 inches of space (women and children were granted slightly less room). By those measurements, the Brooks was able to carry up to 454 slaves. The diagram’s engraver could only squeeze in 400.

Read more in Slave Ship to Freedom Road